Process of splitting off sulphogroups from anthraquinone sulphonic acid derivatives



' Patented Nov, 25,1930

IW EP M nonnnrgnmmyum soi lvi ncr, or ELBERFELD, GERMANY, Assreivon T0 GENERAL 7 k n mus. wonxs mc or nnw YORK, N. Y., A CORPORATION or DELAWARE 9 'rnoonss' on si m mq OFFLSU LrHoGRo Ps I Ihave foundlnew and improvements in processes :of splitting off sulphogroups from anthraquinon'e" sulp'honic racid derivathe other substituents beingomittedi These" tives. g a i i I a a If substituted anthraquinone "sulphonic acids are treated witlrreducing agents two typesoffieductionproducts are obtained, 7 In strongly alkaline: solution leuco compounds care obtainedof whiclrthe generally accepted formulais V leuco compounds revert easilyinto the parent material by oxydation in caustic alkalisolution as for instance by oxygen from the air, they behave like typical yat dyestuffs.

' I have now found thatjby reducing certain substituted anthraquinone sulphonic acids in substantially neutral solutions,i. e., in slight 1y acid, neutral or weakly alkalinesolutions, different reduction products are obtained.

I Such. weakly alkaline solutions are for instance aqueous solutions of soda ash, potassiuln carbonate, pyridine etc. Caustic alkali ammonia etc. may also be used provided, they a p y iv 'ryd solutions? am maybe explained by admitting that one new reduction products, which will belcharacterized further on, are distinguishedfrom the above leuco compounds'by the fact that their alkaline solutions are not readily OXl dized by air t o' form' the parentin iaterialv They are however oxidized in acid solution, a as for instance by means-of persulfats into II the corresponding anthraquinone sulphonio 1 acids. For convenience sake and inas much as we can not assign definite structural formulas tothese novel reduction products I will i I I designate I them by thename hydrocompounds; a q i a j a The leuco compounds can be converted into the hydro-compounds by the action of Weak alkali such as soda ash, pyridine, dilutedoaus.

I tic alkali solutions etc;

I I have furthermore found that these hydrosnort swa ger-Imam sotrnomo lion) DERIVATIVES i a I n; Drawing: Application a April 13, 1926, Serial" no: ioifirso, and mi Ger'niany April 17, iaza compoundswill, with the ,greatestwfaoility, split off one sulpho group, which is eliminat ed as sulphurous acid or a saltthereof. This clearly distinguishes my novel process from heretofore known means of eliminating sulkg 5 pho' groups I from anthraquinone sulphonic acids. The reaction in those cases was one of hydrolysis by which the sulpho group is eliminated in form of sulfuric acid. I i

I This reaction occurs particularly well Wltlll hydroxyglamino substituted amino-anthrai seem to influence materiallythis reaction? I wishit tobe understood thatjunder the term or severalflike or different fof theabove subp stituentsij' y it I a a a A particularly advantageous method of achievingthis reaction is to treatthe hydr0- compounds with alkaline agents. A sulpho group is eliminated in the form of sulfurous acid and an anthraquinone derivative is formed contaln ngonesulphonic acid group less than the original compound. The] reacof the additional hydrogen atoms attaches itself to the SO I-Igroup, which issplitofi' as sulfurous acid, the other one replaces the I so eliminated sulpho group.

of the following type 'n ight be assumed 7' n I] i i i i gSQ L theother substituents omitted: I There. action would thenproceed as follows, the ar- 1 Ihave no exact knowledge of the structural formula of thehydroproduct, but asa nere matter of illustrating the invention a formula "anthraquinone sulphonic acid derivatives as used herein I'fjunderstand such compoundsas J contain at'fleast one of the groups hydroxy, aminoor substituted amino i. e1, alkyl amino,

rows indicating the migration of the hydrogen atoms.

Other desmotrope formulae for the hydrocompounds may be as well justified; it is even possible that the hydrogenation takes place atone of the benzene nuclei; the reaction could then be represented by a graphical equation as follows:

The reaction proceeds in a .very easy and smooth way. It is finished in a few moments and I wish it to be understood that alkalimetal bisulfite and other similar salts are included in the term alkaline agents as used herein.

When starting from pure anthraquinone' sulphonic acids of the type described herein the desulfonated products are obtained directly in a pure and mostly crystalline form.

The ease with which this novel reaction proceeds in dilute acid neutral or weakly alkaline solutions under ordinary conditions constitutes a remarkable technical advance over the heretofore known processes .of eliminating sulpho groups from anthraquinone sulphonic acids. It is furthermore applicable in numerous instances when the old processes fail to work or give rise to undesirable byproducts.

The hydrocompounds can be isolated and obtained in substance, but'it is usually not necessary to do this. The solutions of the hydrocompounds as obtained directly by reducing the anthraquinone sulphonic acid compounds can be treated immediately, with an alkaline agent; this is a very valuable simplification of my novel process.

Anthraquinone sulphonic acids containing several sulpho groups can be so treated as to split off successively one after the other sulpho group. In reacting upon such material with sufficient amounts of a reducing agent and an alkaline agent, the splitting off of the several sulpho groups is achieved in a single operation.

Another convenient reagent which eliminates a sulpho group from the hydrocompounds is concentrated mineral acid, particularly sulfuric acid. Thisreaction is achieved by' dissolving the hydrocompounds in concentrated sulphuric acid and heating this solution. Sulfur dioxide is evolved and when the reaction mass is poured into water the desulphonated product separates. This reaction can be improved by the addition of boric acid. The hydrocompounds are very conveniently obtained by treating the anthraquinone sulphonic acid compounds with alkali metal hydrosulfites, butlother reducing agents as for instance zinc dust in diluted-acetic acid are just as well suited to produce this reaction.

The following examples will further illustrate my invention, the parts being by weight, but I wish it to be understood that my invention is'not limited to the particular substance, nor to the exact reaction conditions mentioned.

Example 1.15 parts of l-amino--hydroxy-anthraquinone-3-sulphonic acid (free acid) of the formula so H oo 3 are suspended in 2000 parts of water and brought into solution by the addition of a solution of 30 parts of crystallized sodium carbonate in 200 parts water. 12 parts of (86%) sodium hydrosulfite (NaS OQ are added to the above solution at room temperature. The violet color of the solution quickly changes to yellow. Addition of about 850 parts of a cold, saturated potassium chloride solution precipitates goldenyellow, beautiful needles, "which constitute the monopotassium salt of the hydrocompound. This precipitate is filtered oil, washed with a little alcohol and dried at low temperature. v

This hydrocompound is dissolved in water and the solution heated on the water bath; pure l-aminol-hydroXy-anthraquinone separates as fine crystals. Addition. of ammonia'or soda ash to the above solution and heating on the water bath speeds up the elimination ofthe sulpho group. If the solution is made alkaline with caustic detected i he: above solutions by acidifying; i V V l i It is, however, not necessary to isolate the hydrocompound as described above. The sodroxyantl1raquinone-3-sulphonic acid is reduced with n sodiumhydrosulphite (Na S OQ V isheated von-the water. bath, and the 1-amino- 4-vhyc lroxy:anthraquinone separates directly Well (crystallized; or if caustic soda is added to thew same solution, its yellow color turns immediately Violet and. the difficulty soluble Sodium l of h l-amino -iiydroxy anr thraquinone separates. l n

400 arts of; {40% sodium bisuilphite Na S0 I solution the sodium salt of the hydrocompoundsepara tes the tormqof Violet-brdwnuneedles; theselar-e'filtered oil,

1 washed with absolute alcohol: and? dried" at low 1 temperature. ".The i hydrocompound is soluble water 1 with a yellowish-red" color, which upon addition of. hydrochloric acid .turns yellow. Byadding soda ash"-to-zay-wa- -t-er solution "oi the 'hy drooonnpoundg Fand heating ronfthe water bath, the yellow-ish red it the rhydmocompound, soon separates:

-sulpho 1 group i is split oil" at ordinary item color tunns "violet-blue "and the p-diamino- 1anrthrarufin-monosulphonicl "acid, obtained the splitting of? of a rsulpho group i from The x per-attire if caustic soda is 1 addedto the wazter solution of the hydrocom-pound; i

s jlnAsUih aswbeen stated heretotore i-t is not necessary to isolate: the hydrocompound.

27 parts of caustic-soda solution (33%) are 7 addedwdirectly at room temperature to the i it reduction liquor as obtained a ove; the

color otthe solution changes from red to a ygreenisheblue and the sodium salt of the monosu-lphonic :Sl-Cld quickly separates; 1 1 It n is filtered elf, washed, 2 dried and identified e n i n l Ewample 3.--.-10

pound: of the p diamino;anthrarufin disulin theusual way. i

1 5mg f the hydratephonic acid asobtained accordingzto EX ample2-are dissolv edin lfidparts ofeo-ncentrated "(sulphuric acid, .5; parts [of :boric acid-are added, andthe mama heated; ion

the: waterabath; Tlie ayellow color:of 1 the s0 lutiori gradually tuuns blue and sulphur: {diohange any more thereaction mass is poured E mwmple .4.The hydrocompound ofthe i amino-4-hydroxy-anthraquinone-3-sulphonic.

acid obtained'according to Example 1 is dis solved in concentrated sulphuric acid and with addition ofborie acid heated onthe water bath, theworiginallyfyellow color of the solution turns bluish-red with a vermillion red fluorescence, indicating the formation of the 1%4 amiIiO hydrOX'y anthraquinonei This is isolated intlieusualw aya 1 i b Example p diamino-anthrarufinbnlono=6 sulphonic a'cidas obtained in Exam ple-Q is dissolved -inwater and sodium hydrosulphiteKNags Og) added until the color of the solution has taken a yellowish-red color. f sodaash is now addedtoulthi's solution and i heated on the waterbatlii The colorchanges' 1 quickly to aviolet andja" brownish-violet pre- 2 1 t 'cipitateseparates,wl1ich issubstantiallypure are dissolved in l00o parts of hot wateiaf "std this 9 blue 1 solution; the color changes to an o-range-yellow- Uponadding o of p-uiamim-m thrai'uiin-disulphoni'e acidgare dissolved in '20OO pa 1'ts ofwater and asolution'of parts of crystallized sodiurnc'arbonate 111200 parts hydrosulphite NaQSQOQ are now quickly introduced and the yellowish-red solution obtained heated on thewater bath. The color of the solution soon turns a violet and a brownishwiolet precipitatefseparates. The heating is continued for 3-4;, hours and after the cooling, theprecipitate filtered oil. It is then boiled in' dilutecl caustic soda solution,

acidified and the precipitate filtered off; it consists of yery pure p-dialninosanthrarufin.

EQramplerZfilO parts of p-diniethylamino- M eWfiR-YZ-G e as 19 i? h forwhile stirring; "3,8 parts of sodium hydrosulphite (Na S OQ added. -The greenish-blue (solution it immediately beeomesZ orange with Y formationof the hyd rocompound containing two additional hydrogen atoms; itcan easily are disease 200' parts ofwa mharase y betobtainedxin solidform salting out this resolution. let partsl caustic soda solution of 33% strengthare nowladded; thepcolorpof Lthe solution turn s; sblue I and the ,nxonosuL sodium chloride.

phonic acid begins to separate. a The pre-- cipitation is completed by the "addition of The free monosulphonic acid can also be obtained by acidifying the hot solution. The compound obtained has most likely the formula:

H Ewample 8.- parts p-dimethylaminoanthrarufin-disulphonic acid are dissolved at in 1100 parts of water containing 30 parts of crystallized sodium carbonate. '25 parts of (82%) sodium hydrosulphite (Na S O are then added, the color of the solution changing from greenish-blue to orange. The temperature is now increased to 80 (3., a solution of parts of crystallized III OH OH N In the table below additional anthraquinone compounds are given, which have been obtained by the use of my invention, from their corresponding sulphonic acids:

sulphonic acid Products obtained Quinizarine-Z-sulphonic acid Quinizarine. Purpurinc-Bsulphonic acid Purpurine. AnthrarufimZ-fi-disulphonic acid... Anthrarufine.

1 amino anthraquinone 2 su1- phonic acid.

1 5 diamino anthraquinone 2 G-disulphonic acid.

1 5 diamino anthraquinone 2 6-disulphonic acid.

1 amino 4 bromoanthraquinone- Zsulphonic acid.

Lamino-anthraquiuone.

l 5 diamino anthraquim one-2-sulphonic acid. 1-5-diamino-anthraquinone.

1 4 amino bromo anthraquinone.

The 1-5-diamino-anthraquinone-2-sulphonic acid is hardly obtainable by any other process than the one described herein.

The p-diamino-chrysazine-2-7-dishulphonic acid as well as the p-diamino-anthrarufine- Q-T-disulphonic acid when subjected to my novel process will produce the corresponding sulphonic acids or diamino-dihydroXy-anthraquinone.

The term hydro compounds used in the claims is intended to comprise the compounds obtainable by reducing the substituted anthraquinone sulphonic acids in a substantially neutral or weakly alkaline solution as more fully described in the specification. The hydro compounds are distinguished from the corresponding leuco compounds by the fact that their alkaline solution is not readily oxidized by means of air to formthe parent material. Furthermore, they will, with the greatest facility, split off a sulpho group which is eliminated as sulfurous acid or a salt thereof. 4

I claim: i

1. The process of splitting oif a sulpho group from an anthraquinone sulphonic acid derivative which comprises treating the anthraquinone sulphonic acid derivative in a substantially neutral solution with sodium hydrosulfite whereby there is formed a hydrocompound of said anthraquinone sulphonic acid derivative, and treating the said hydrocompound with an alkaline agent.

2. The process ofsplittingofi' asulphogroup from an anthraquinone sulphonic acid derivative which comprises treating the anthraquinone sulphonic'acid derivative-in a substantially neutral solution with sodium hydrosulfite whereby there is formed a hydrocompound of said anthraquinone sulphonic acid derivative, and treating the said hydrocompound with a solution of caustic soda.

3. The process of splitting off a sulpho group from an anthraquinone sulphonic acid derivative which comprises treating the anthraquinone sulphonic acid derivative in a substantially neutral solution with an alkali metal hydrosulfite whereby there is formed a hydrocompound of said anthraquinone sulphonic acid derivative and treating the said hydrocompound with an alkaline agent.

4. The process of making an alpha-di methyl-amino alpha dihydroXy-anthraquinone monosulphonic acid which comprises reducing the coresponding disulphonic acid to form a hydro-compound by heating the same in aweak hydrosulfite solution and then splitting off one sulpho group by the addition of an amount of caustic soda such that the solution contains about 2% thereof.

5. The process of making an alpha-dimethylamino-alpha dihydroxy anthraquinonc monosulphonic acid which comprises reducing the corresponding disulphonic acid to form a hydro-compound by heating the same in a weak hydrosulfite solution and then splitting off one sulpho group by the addition ofan amount of an alkaline agent such that the solution contains about 2% thereof; the solution having a temperature not greater than about 60 C. during the two steps.

6. The process of making hS-dimethylamllO ino 1.5 dihydroxy anthraquinone monosulphonic acid ofthe formula which comprises reducing 4.8-dimethy1amino-l.5-dihydroxy anthraquinone 2.6-dis111- phonic acid to form a hydro-compound and heating the latter, at about 60 C. in an alkaline solution containing about 2 percent of at about 60 C. and precipitating the reaction caustic soda. 7 V

7. The-process which comprises dissolving 10 parts of p-dimethylamino-anthrarufine-2- 6-disu1phonic aoidin 200 parts of Water, addingwhile stirring 3,8 parts of sodium hydrosulfite, at a temperature of about 60 C. until. the solution becomes orange, thereafter adding 14 parts of caustic soda solution of 33% strength While maintaining the temperature product by the addition-of sodiumchloride.

In testimony whereof I have hereunto set "my handw Y EMANUEL SCHMIDT,

ROBERT 

